Balancing apparatus



Nov. 28, 1961 M. G. KONING BALANCING APPARATUS Filed Dec. 22, 1959 mm mm INVENTOR. MENNO G. KONING KENWAY, JENNEY, WITI'ER 1 HIl-DIP' ATTORNEYS United States Patent 3,010,326 BALANCING APPARATUS Menno G. Koning, Dover, Mass assignor, by mesne assignments, to Northrop Corporaton, Beverly Hills, Calif., a corporafion of California Filed Dec. 22, 1959, Ser. No. 861,355 10 Claims. (Cl. 745.4)

The present invention relates in general to new and improved apparatus for halaneing a gyro and in particular to apparatus for balancing a gyro gimbal from the outside of a sealed housing in which the gyro is disposed.

In a gyroscope which is destined for a gyro-controlled system, it is important that the gyro gimbal (or grnbals) be perfectly balanced about the gimbal rotation axs in order to prevent gyro drift which rnay afect the accuracy of the entire system. This is particularly the case when the gyro is used in a navigation systern or the like, where such an error may have a cumulative eiect. t is extremely difiicult to machine the gyro components to obtain perfect gimbal balance due to hurnan limitations as well as due to the limitations of the machine tools used in the rnanuaeture of the gyro components. Accordingly, gimbal balancing means are frequently provided in conjunction with each gyro in order to remedy this defect. In general, these balancing means attempt t position a mass which is adapted to :rotate with the gimbal in order to shift the gimbal center of gravity.

Presently available gyros which are so equipped enjoy only limited success since they require direct access to the balancing means and to the girnbal. Under these conditions, a proper gimbal balance is obtained prior to the time when the gyro is enclosed in its housing. lf, as is requently the case, the gyro is positoned in an hermetically sealed housing filled with a viscous fiuid, ready access to the balancing means is no longer possible. Any subsequently occuning unhalance, e.g. gimbal unhalance due to the repeated solidification and liquefacton of the viscous fluid with ambient temperature changes and its effect en the delicate gimbal suspension, cannot be corrected other than by breaking the hermetic seal and draining the fluid.

Prior attempts at overconfing this dificulty have resulted in elaborate constructions which have materially increased the difiiculty as Well as the expense of gyroscope manufacture. The overriding disadvantage, however, of such apparatus has been the addition of considerable bulk and weight to an instrument which must generally be kept as small and lght as possible. A typical construction which is representative of the prior art, is disclosed in Patent No. 2,707882 and employs a Hermeflex unit for transmitting rotary motion through a sealed wall. This arrangement requires not only a airly complicated construction, but also adds a substantial amonnt of weight and bulk to the gyro which seriously detracts fi'0111 its overall utility.

Accordingly, it is the primary object of the present invention to provide improved apparatus for halancing a gyro girnbal from the outside of a sealed housing in which the -gyro is disposed.

lt is another object of this invention to provide apparatus for externally balancing the gimbal of a sealed gyro, which is simple in construction which adcls only a minmal amount of weight and bulk to the gyro.

In accordance with the inventon which forms the subject matter of this appfication, the foregoing objects are carried ou-t by providing at least one balancing mass which is resiliently urged against the gyro gimbal in an axial direcion. Hermetically sealed access means in the form of bellows are spaced about the gyro casing 3,010,326 Patented Nov. 28, 1961 ice and permit the manipulation of the balancing mass without breaking the hermetic seal. Positioning of the balancng mass relative to the gimbal rotation axis in a plane normal to the latter may thus be carried out against the action of the continuously applied, axial resilient holding force.

These and other objects of this invention together with urther features and advantages t=hereof will becorne apparent from the following detailed specification when read in conjunction with the accompanying drawings in which:

FIG. 1 is an elevation view of the -pertinent portion of a gyro which embodies the present invention;

FIG. 2 is a view taken along line 22 of FIG. 1;

FIG. 3 llustrates a preferred emhodiment of a clamping plate; and

FIG. 4 illustrates a balancng bar for use with the clarnping plate of FIG. 3.

With reference now to the drawings, an hermetically sealed housing 10 is seen -to contain a gimhal 12 in the form of a shell which is completely surrounded by a viscous fluid 14. The base 16 of the gimbal shell, which is substantially normal to the gimbal rotation axis 18, includes a construction adapted -to hold a pivot 20 in alignment With the gimbal rotation axis. 'Ihe pivot 20 rides in a jewel pivot hearing 22 which is ultimately supported by the housing 10.

A clamping plate 24 is affixed by means of screws 26 to the base 16 of the igirubal shell 12. The clamping plate 24 is illustrated in greater detail in FIG. 3 and is seen to consist of an annular ring having a central opening 28 to accommodate the pivot hearing structure, as well as a pair of perpendicularly intersecting grooves 30 and 32. The holes 34 accommodate the serews 26 (see FIG. 1) for aiixing the clamping plate 1:0 the gimbal shell, While the holes 36 selectively accommodate set screws 38 whose mass is used to provide a rough gimbal balance.

The perpendicularly intersecting grooves 30 and 32 of the clamping plate 24 permits sliding motion of a pair of balancing bars 40 and 42 which are disposed between the clamping plate and the gimbal base 16. The balancing bars are illustrated in greater detail in FIG. 4 and are seen to contain an elongated eentral slot 44 which clears the pivot hearing structure. Bach balancing bar further comprises a central portion 45 which terminates in a pair of raised end portions 46. The latter are seen to extend beyond the -perimeter 0 the clampng plate 24 and of the gimbal base 16 when the balancing bars are in clamped position (see FIG. 1). The central portion 45 of each balancing bar is siightly eurved so that the baiancing bar curves out of the plane of the clarnping plate in its unclamped condition. In order to permit a sliding rnotion of the balancng bars in their correspondng grooves without interfering with each ether, the raised end portions 46 are so arranged in the grooves that the respective -central portions 45 are disposed in ditferent planes. In this position the balaneng bars are resliently clamped against the gimbal base 16 by the action of the clan1ping plate 24.

The housing 10 further contains an access opening 48 corresponding to each one of the protruding balancing bar portions 46 and aligned therewith. A hub plate 50 is positioned in each access opening, an extensible bellows 52 being sealed thereto and extending interiorly of the housng 10. The bellows 52 terminates in a 1igid end plate 54 which is sealed thereto. The hub plate 50 further includes a tapped hole which accommodates a mating screw 56 that extends into the bellows a suificient distance to contact the end plate 54.

lf it is desired to adjust the gyro glmbal balance, all but one of the screws 56 are partially withdrawn in order 3 to pennitiree motion of theincorresponding end plates. The remaim'ng screw is further inserted until its contaoting end plate applies a force aganst the balancing bar end-pcntgion -46 which is aligned with it. Simultaneously the extension of the bellows surroundingthe inserted screw causes a displacement of the vscous fiuid which tends to compress the bellows in the other portionsof the housing. Any further forward motion of the inserted screw cause s its corresponding end plate to bring forceto bearagainst the protruding end portion 46. Huis force is suficient to displace the balancing bar relative to the gimbal axis, against the-holding action of the avially.applied resilient foree clarnpng it tothe gimbal. It will be noted that, since the baancing bars are constrained to move in their correspondng grooves, they may only be positioned in a plane normal to the gin1bal rotation axis. Proper gimbal balancing may thus be obtaned by positioning the two balancing bars in their corresponding -grooves and thereby -shiftng the efective center of gravity of the gimbal. It will be understood that the positioning screw 56 must be partially withdrawn-in each case if a displacement of the same balancing bar in the opposte direction is to be carned out.

When proper baiance has been obtained, the screws 56 are withdrawnto an extent where the end plates are out of contact with their corresponding balancing bars. Bach screw is loeked in place by suitable locking means in a position where the corersponding bellows 56 is partially extended and the end plae 54 is held rigidly in place. Where balaneing screws have been used, the

screw heads Will extend asubstantiafl distance outside of the sealed housing 10 in this position. If the hermetieally sealed housing includes an additional protective cover 58 which cannt accommodate the extending serews 56, the latter are replaced by shorter screws which do not extend materially beyond the housing but whichstill maintain thebellows in an extended position by applying force against the end ;ilate 54.

It will be understood that the invention herein is not confined to the illustrated embodment. For example, rit is not necessary to nse a screw in order to manipulate the balancing bars. Any elongated rod-like structure which fisthrough the threaded hole in the hub plate 50 may be employed in order to cause the end plate 54 to apply force to its corresponding balaneing bar. It is only necessary that suficient force be app lied in order to displace the ballancing bar against the acton of the axially applied resilient clamping force which must be snflciently high to held the balancing bar in place during any maneuver to which the gyro may be subjec-Led.

The illustrated embodirnent of the inventon shows balaneing =apparatus which is capable of independently adjusting the balance of a gyro in two mutually perpendcular planes. By the use of addition-al balancing bars this construction may be modified to provide an independent adjustrnent in more than two planes. It is also possible to use a single balancirtg mass, e.g. in the fonn of an annular disk, in place of the separate bal ancing, bars, suitable points being provided on the disk for the application of force through the bellows. Snch a disk requires a central opening sufiiciently large to accommodate the pivot hearing structure while still permtting movement in a plane normal to the g-imbal rotation -axis. In such a case the resilient clamping force is preferably dne to the spring-like construotion of the clarnping plate itself. If desred, such an arrangement may be further modified to provide the claniping plate and the balancing disk with a m-ating construction t0 permit only rectilinear dsplacement 0 the disk.

From the -oregoing disclosure of the nvention it be apparent that numerous modifications, departures and eqnivalents will now occur t0 those skilled in the art, 211 of which fall Within the true spirit and scopeof this invention.

1. Apparatus for adjusting, the balance of a gyro gimbal about the gimbal rotation axis externally of a sealed housing in which the gyro is disposed comprisng, clamping means, balancing means po-stioned between said gimbal and said clampng means, said claxnping means cooperating with said balaneing means to dlamp the latter res-liently against said girnbal, sealed, flexible access means disposed in said honsing, said access means permitting the applicationof force to said balancing means to displace the latter relative to said girnbal.

2. In a gyro disposedin an hermetically sealed, fluid filled housing means for externally adjusting the balance of the gyro -gmbal about the gimbal rotation axis comp;ising a clamping plate afixed t0 said gimbal substantially normal to said girnbal rotaton -axis, a pair of resilient blancing bars slideably postoned between said clampingplate and said girnbal and resil-iently nrged against the latter, said balancng bars being disposed at right angles-to each ether] and extending beyond said clarnpingplate and said gimbal, a plurality of openings in said housing aligned with said balancing bars, a bellowsradially extending into said housing from each of said openings and providing an hermetic seal, and means for applying force through said bellows to said balancing bars to position the later in a direotion normal to said gimbal rotation axis.

13. Apparatusfor adjusting the balance of a gyro gimbal about the grnbal rotaeion axis externally of a sealed housing inwhich the gyro isdisposed comprising, a

clarnping plate aflixed to said gimbai in a plane substan- .t ally norrnal to said gimbal rotation axis, balancing means adapted to be resiliently clamped against said gimbal by said clarnping plate, a pluralty of openings in said honsing each ineluding a flexible, sealed bellows extending nto said housing, and means for postioning said balancing means relative to said gimbal by manipulation through said bellows.

4. In a gyro positioned in a sealed housing and ncluding a girnbalrotatably disposed about a gimbal rotaton axis, means for resiliently holding at least one balancng weight in contact with said giznbal, sealed access meatis disposed in said housing, said access means being adapted to permit external positioning of said balancing weight in -a plane normal to said g.mbal rotation axis.

5. In combination with a gyro positioried in a sealed housing and including =a gimbal rotatably disposed about a gimbal rotation axis, means for resilienfily holding a plurality of balancing weightsin Contact with said gimbal, sealed expansble means spaced about said housing to provide access to the interior thereof, said sealed expansble means -beng adapted t0 permit thepositioning of said balancing weights in a plane normal to said gimbal rotatonaxis.

6. Apparatus for adjusting the balance of a gyro gimbal :about the gimbal rotation axis exterhally of a sealed housing in which the gyro is disposed comprising, a clamping plate aflxed to said gimbal in a plane substantially normal to said gimbal rotation axis, a plurality of balancing meansadapted to be resiliently clarnped against said gimbal by said clamping plate a plurality of openings in said housing each including a flexible, sealed bellows extending into said housing, and means for independently positioning said balancing means relative L0 said gimbal by manipulation through said bellows.

7. Ina gyro positioned in a sealed housing and including a girnbal rotatably disposed about a gimbal rotation axis, means for resiliently holding a plurality of balancing weights incontact with said gimbal, sealed .access means disposed in said housing, said access means being adapted to permit independent external positioning of said balancingweights in a plane normal to said girnbal rotation axis.

8. In vcombination with a gyro positioned in a sealed housing and including a gimbal rotatably disposed about a girnbal rotation axs, means for resiliently holding a plurality of independent bancing weignts in contact with said gmb, sealed expansible means spaced about said housing to provide access to the interior thereof, said seaied expansible means being adapted to permit the i11- dependent positioning of said balancing weigbts in a plane normal -to sad gimbal rotation axis.

9. In a gyro disposed in an hermetically sealed, fluidfiHd housing, said gyro includng a gimbal rotatably supported in a pivot hearing aligned with the gimbal rotation axis, rneans for adjustng the balance of said gimbal about said grnbal rotation axs eompn'sing, a clamping plate affixed to said gimbal substantially normal to said gmbal rotation axis, said clarnping plate including a plurality of grooves facing said girnbal, a resilient balancng bar slideably disposed in eaeh of sm'd grooves and adapted to curve out of the plane of said clamping plate, said clampng plate resilienty urging saicl balancing bars against said gmbal, said balancng bars being centrally slotted to clear said pivot hearing and extending beyond the perimeter of said c1ampng plate and said girnbal, a plurality of openings circumferentially spaced about said housing and aligned With said balancing bars, a sealed bellows extending into said housing frorn each of said openings, and means for applying force to said balancing bars through said bellows to dsplace said balancing bar relative to said gimbal rotation axis.

10. In a gyro disposed in an hermetically sealed, fluidfilled housing and havng a gimbal rotatably supported in a girnbal hearing aligned with the gimbal rotation axs, sad gimbal including a gimbal shell, means for externally adjusting the balance of said gimbal about said gimbal rotation axis comprising, an annular clamping plate af fixed to said girnbal shell substantially concentric with said gmbal rotation axs and in a plane normal thereto, said clarnping plate incluing a pair of perpendicularly intersecting grooves acing said gimbal shell, a pair of resilient balancng bars disposed in said grooves so as to mantain sliding clearance from each other, said balancing bars curving out of the plane of said clamping plate and adapted to be resiliently clamped against said gimbal shell by said clamping plate, each of said balancing bars having a c6ntral slot adapted to clear said pivot hearing and further includng a pair of end portions partially protruding beyond the perimeter of said clamping plate and said gin1bal shell, said honsing having an opening positioned opposite eacl1 of sacl protruding end por-dons, a hub plate disposed in eacn of said openings including a tapped hole, an expansible bellows sealed zo said hub plate and extending interorly of said housng, said bellows terminating in a rigid end plate sealed thereto, a threaded shaft mating with said tapped hole and extending into said bellows to contact sad end plate, sad shaft being adapted to urge said end pla-te against its oppostely positioned protruding end portion in order to displace the corresponding balancing bar.

References Cited in the le of ths patent UNITED STATES PATENTS 1,398,692 Beattie Iuly 1, 1919 2650502 Lundberg et al Sept. 1, 1953 2,707,882 Kent May 10, 1955 2,780,940 Brown Feb. 12, 1957 2,855782 Grohe Oct. 14, 1958 

